Ever greater attempts have been made in recent times with magnetic resonance scanners, under the impetus of technical development in computer tomography, to use shorter main field magnets in order to thereby achieve a more open embodiment of magnetic resonance devices. Such shortening of the magnets for magnetic resonance scanners offers the advantage that access to the patient is facilitated during production of image recordings or when performing measurements and between individual recordings. In addition a patient's feeling of claustrophobia or even feelings of anxiety which frequently occur during the examination can be avoided. In addition, the shorter embodiment of the magnet in the z-direction, i.e. in the direction of the longitudinal axis of a patient support table, counters the increasing cost pressures arising during manufacturing of the scanners, since the scanner costs are definitively determined by the magnet costs. These magnet costs can be significantly reduced by a reduction of the material and a simplification of the magnet structure.
Despite innovative construction concepts for the magnets or the magnetic resonance devices, making the magnet shorter is frequently connected with a shortening of the area with a homogeneous magnetic field. This has meant that in recent times there has been evidence, with a number of newer systems, of a markedly shorter field-of-view available for image recording.
The shortening of the area with a homogeneous magnetic field in the z-direction produces problems however, if tilted or even double-tilted layers are to be recorded, as is required for example for spinal cord images and specific heart images. With an extreme shortening of the magnet the homogeneous magnetic field area available in the z-direction is no longer sufficient here under some circumstances to produce measurements with the required quality and expressiveness.
An arrangement for magnetic resonance imaging is known from WO 01/70109 A1, in which the opening has a diameter which is significantly greater than the axial length of the opening. After the patient has been placed in the opening, a relative rotation between the patient and the magnet arrangement can be undertaken, for the purposes of which the magnet arrangement is tilted or rotated respectively around a horizontal axis or the patient is subjected to a corresponding horizontal inclination or rotation, as is indicated for example in FIGS. 6 to 13 of this document.
JP 2001 046355 A relates to a device for creating a magnetic field, in which a rotational force can be exerted on a horizontal axis. A rotation actuator can also be used to exert a rotational impulse on a vertical axis which is connected to a support arm.
A device for creating a magnetic field is known from JP 611 141 148 A in which a linear motor is provided for movement of the magnet arc.